To promote weight saving of jet engines, a titanium compressor case and titanium rotor blades, both of which are composed of titanium alloys, are applied to compressors of the jet engines.
On the other hand, for prevention of titanium fire caused by mutual friction between an internal surface of the titanium compressor case and a tip end portion of the titanium rotor blade, by using a soft material such as Ni-graphite as a spraying material, a porous abradable coating having abradability is formed on the internal surface of the titanium compressor case by spraying. Here, the term “abradability” means a quality of being abraded with respect to a member where the member is abraded by an opposite member having relation of mutual friction with the member, and the abradable coating is easily abraded by the rotor blades having relation of mutual friction.